The present invention relates generally to metallic food containers that may be used for cooking dough or pastry based foodstuffs in either a microwave oven or in other types of conventional ovens.
As noted in prior U.S. Pat. No. 4,558,198, for example, previously it has been generally believed that metal containers should not be used to heat or cook food in microwave ovens. Bare metal containers can reflect the electromagnetic energy emanating from the magnetron tube (which supplies the energy for cooking to the oven cavity) and thereby damage same. In addition, when bare metal is disposed in close proximity to the metal walls of the microwave oven, electrical arcing may occur between the container and the oven walls. For these reasons, the industry has generally advocated using only containers of plastic, cardboard or other non-microwave reflective material to heat loads, e.g. food, in microwave ovens.
It is also known that certain exceptions to the prohibition against use of metal containers in microwave ovens are from time to time desirable. For example, to shield one food portion from another in a container and thereby effect differential heating and cooking thereof, metal containers or metallic portions thereof have been utilized to effect differential microwave energy input to the various food portions to be cooked. This has been accomplished by the use of metal containers having relatively deeper and shallower portions, for example, and/or metal strips or other shielding materials. Ferrite materials, for example, absorb microwave energy and thereby cause the metal to be heated such that cooking or heating of food in the metal container portion is effected at least in part much as it would occur in a conventional, convection or infrared radiation oven.
The above cited U.S. Pat. No. 4,558,198 discloses a metal container and system for arc-free microwave cooking and minimal reflection of electromagnetic radiation. These benefits are achieved, according to the patent, by means of structural refinements in a metallic container, including provision of smooth, wrinkle free side and bottom walls and edges, a physical geometry incorporating generous radii in lieu of sharp corners in the container structure, a coating of heat resistant plastic material of a specified film thickness on both sides of the walls and the edges of the container to diffuse microwave radiation, and a heat resistant microwave transparent lid or dome for the container.
A great many more patents address these and various other problems that have been identified in the art of microwave cooking. For example, United Kingdom Patent Specification No. 1,593,523 discloses a container for a differential heating system which comprises an open-top, tray-like body which holds one or more predetermined food items to be heated in a microwave oven, and a cover for closing the tray, with the tray and cover being formed overall from material which is transparent to microwave radiation, and having disposed thereon a layer of microwave radiation opaque material or shielding material on the parts thereof which correspond to portions of the container whose contents require reduced microwave radiation exposure during cooking. U.S. Pat. No. 4,283,427 discloses a microwave heating package incorporating a lossy chemical susceptor that is initially microwave radiation opaque but becomes substantially microwave transparent upon extended exposure to microwave radiation. U.S. Pat. No. 4,190,757 discloses a microwave heating package and method including a shield such as a foil sheet which reduces by a predetermined controlled amount the exposure of the package contents to microwave energy, the shield having openings or apertures of predetermined size to provide controlled exposure of the contents to microwave energy.
U.S. Pat. No. 3,219,460 discloses a frozen food package having a dielectric cover which overlies a shield of such material as aluminum foil, and which shield is disposed atop the package container directly beneath the top or lid therefor. The shield incorporates apertures of predetermined number, area and pattern to provide an unshielded area which permits cooking energy to penetrate into the container. U.S. Pat. No. 4,317,017 discloses a steamer for use in a microwave oven and wherein a water reservoir in the bottom of the steamer container is exposed to microwave radiation for heating of the water to produce steam. The foodstuffs to be steam cooked thereby are shielded from exposure to microwave radiation.
U.S. Pat. No. 4,351,997 discloses yet another food package comprising a tray having at least inner surfaces of the walls and rim thereof coated with microwave radiation reflecting or opaque material whereas the bottom is of microwave radiation transparent material. U.S. Pat. No. 3,854,023 and 3,985,991 disclose microwave cooking utensils which utilize metal (i.e. shielding) containers inside radiation porous closed containers to produce, condense and recycle steam by absorbing condensation and transporting it away from the low temperature surface that promotes condensation and to an elevated temperature zone for reproducing steam, this to provide improved cooking through control of the pattern of heating by use of the vapor evaporation/condensation cycle in a closed container.
U.S. Pat. No. 4,560,850 provides disclosure similar in many respects to that of the above cited U.S. Pat. No. 4,558,198, and additionally discloses a central steam port for use with a covered microwave cooking container to produce an escape passage for steam evolved during cooking of the contents, which steam then passes over surfaces of the container to heat same and thereby convey the heat energy to the foodstuffs being cooked.
Other patent references that are generally pertinent to microwave cooking techniques include U.S. Pat. Nos. 4,027,132;3,547,661;4,306,133;2,714,070;3,985,990; and 4,390,554.
In spite of extensive efforts directed toward improvement of microwave cooking systems there remains a need in the art for containers well suited for cooking of dough or pastry based foodstuffs in microwave ovens. Many such foodstuffs are packaged and sold in bare (uncoated) aluminum containers which are not suitable for microwave cooking. Prior efforts to provide packages for dough or pastry based food stuffs that are better suited for microwave cooking have produced uneconomical results and/or cooking procedures of undue complexity. There remains in the art a need for a disposable, combined food package/cooking container of economical construction which will permit simple and effective cooking of dough or pastry based foodstuffs in either a microwave oven or other conventional ovens.